Iron and steel products and process of producing the same



Patented May 23, 1944 IRON'AND STEEL PRODUCTS AND PROCESS OF PRODUCINGTHE SAME James C. Hartley, Norwalk, Conn., and Otto H. Henry, Caldwell,N. 1., assignors to Minerals and Metals Corporation, New York, N. Y., acorporation of Delaware No Drawing.

10 Claims.

This invention relates to the production of iron and steel productscomprising in their composition elements which, if present underordinary conditions of iron and steel manufacture. would deleteriouslyaffect the quality or even render commercially valueless iron and steelproducts containing them, but which, when contained in the novelproducts of the present invention produced by the novel process of thepresent invention, not only do not have any deleterious eifect upon theproducts but in many cases improve the qualities of the products forcertain uses.

The invention relates particularly to avoiding the deleterious effectsof the presence, in

iron and steel products, of elements of the group commonly to be foundin iron ores, such as phosphorus, sulfur, silicon and titanium, whensuch ones are reduced and the resultant iron is manufactured into. ironand steel products by the processes commonly employed, and at the sametime to take advantage of-the beneficial effects of the presence of oneor more of these elements in iron and steel products, when introducedunder certain conditions which are provided for by the practice of thepresent invention.

In the manufacture of iron and steel articles by the processes generallyemployed at the present time, which involve the reduction of the ironore in the blast furnace and subsequent operations of melting andrefining the ore in the open hearth furnace, Bessemer converterorelectric furnace, it, has long been known that, if the elements abovereferred to, or compounds thereof, are present in appreciable quantitiesduring the aforesaid stages in the production of iron and steelarticles, these elements, and particularly phosphorus, silicon andtitanium, tend,

to 'reduce to the elemental form and tend to go into combination withthe iron, either in the form of solutions of the elements in the iron orin the form of chemical compounds thereof, with the result that theymaterially impair or alter the physical characteristics of the finishedproduct. .If sulfur be present in the ore in appreciable quantities orif it be present in the coke used in the reduction, or in the fluxes, orin the refractory linings of any of the furnaces, it forms with the irona eutectic mixture, known as the iron-iron sulfide eutectic, which has afreezing point lower than that of the pure iron or steel. When,therefore the manufacture of an iron or steel product involves a meltingstage, then, upon solidification of the iron or steel product, thisiron-iron sulfide eutectic mixture, which Application December 7,, 1940,Serial No. 369,052

freezes last, will be crowded out of the matrix of the material and willbe forced to segregate around the grain boundaries of the material, thusweakening the final product and, moreover, because of its low meltingpoint, causing the condition known as hot shortness to exist in the ironor steel.

The property of iron and steel commonly termed "hot shortness is usuallyunderstood to mean a lack of ductility or workability at ordinaryforging, hot rolling or otherwise deforming temperatures and isapparently caused by the distintegration or softening of the iron sulndeconstituent under the heat of the forging, rolling or other deformingoperation. To avoid this property in the final product, it is necessary,in normal steel-making practice, to supply a considerable amount ofmetallic manganese in"'the steel bath in order to form a manganesesulfide compound with the residual sulfur and thus prevent the formationof the iron-iron sulfide eutectic. The manganese sulfide thus formed toa great extent enters into the slag but a conslderabl proportion of itremains mechanically entrapped in the steel where, having a freezingpoint higher than that of the iron and steel and thus solidifying first,it is not segregated or driven to the grain boundaries of the steel butrather remains as individual inclusions and thus does not materiallyaffect any of the physical characteristics of the finished product.

When phosphorus, silicon and titanium are present in appreciablequantities in steel which has been molten and which has been maintainedat temperatures suficiently high and under conditions suflicientlyreducing to reduce the compounds of phosphorus, silicon and titaniumwhich are found in the ores or in other materials with which the oresare associated during reduction, these elements, when thus reduced, tendto go into solution in the iron and also, in certain cases.

'to form chemical compounds which cause embrittlement and lack ofstrength in the finished product, Phosphorus, in particular, creates inthe finished product a condition known as cold shortness, which isevidenced by a lack of ductility in the finished product at ordinarytemperatures and which prevents the cold rolling or cold working of ironand steel containing appreciable amounts of phosphorus.

Thereis no simple treatment which will effect the immobilizing-ofphosphorus, silicon or titanium such as the manganese treatment forsulfur. It has been found in practice, therefore, that the phosphoruscontent in finished steel,

comprising, in their compos'ition,.the elements 7 hereinabovespecifically mentioned, without any deleterious eifectupon the qualityor commercial value of the iron and steel products by reason of thepresence of these elements, but it has also been found that otherelements, which are soinetimes associated with iron ores and which, ifchemically associated with the finished iron or steel product, tend toimpair or change the physicai characteristics thereof, may also berendered inocuous by the practice of the present invention.

An important advantage of the present invention is that it makespossible in the manufacture ofiron andsteel products, and particularlyin continuous processes to this end, the utilization-of iron oreswhichpby reason of the impurities contained therein which are notreadily removable or which tend to cause trouble during. the reductionor fabrication of the iron, have heretofore been considered-unsuitableOr uneconomical for commercial use. Among the orcs of iron-or steelwhich have been found to have commercial utility when employed in themanufacture of ironzor steel products embodying and made by the processof the present invention,

are the ilmenite beach sand ores and the other ores-high in titaniumwhich have not been used p to the present time to any great extentbecaus of their high titanium content; the high sulfur ores,particularly those containing pyrrhotite, and the high phosphorus ores.

1 Other objects and important advantages of the invention willappearfrom the follow ng description of the practical application bf theinvention to themanufa'cture of iron and steel products. In the,practiceof the present invention it has been found that if iron ore be reducedby means of a direct reduction-process such ,as described in theco-pending application of He {man A. 'Brassert, Serial No. 323,076,filed March 9, 1940, Manufacture of metal products, by which a fine- 1)divided ore, either mixed with finely divided carbon or without havingcarbon added thereto.

is supported upon a perforated hearth and inde-,

pendently agitated while a reducing gas is passed through the hearth andth ough the ore supported thereon; or in the co-pending application ofJames C. Hartley. Serial No. 338,560, filed June 3, 1949, Process of andapparatus for facilitat ing and controlling chemical reactions andphysical treatments, by which a finely divided ore,

supported on a hearth having inclined jet orifices, is both agitated andreduced by passing a heated reducing gas through said orifices with Isuflicient force to effect the agitation of the ore and its movementover the-hearth; 'orin the co-- pending application of James C. Hartley,Serial No.- 339,095, filed June 6,. 1940, Process of reducin: metallicoxides, by which a'finely divided con- *centrated ore, either coated .orimpregnated with h a finely divided carbon, is substantially completelyreduced by'raising it tothe reduction temperature and effecting anagitation thereof; The 75 reduced ore is then further concentrated byreducing its temperature to the magnetic rangeand effecting a magneticconcentration thereofand the concentrated reduced ore is then subjectedto a further reduction treatment by means of a gaseous reducing agentwhich effects both the agitation and the reduction thereof, and if, asoutlined in said .copending applications, the reduction temperatures bemaintained below the 10 temperatures a which the oxides or compounds ofthe elemcn hereinabove mentioned, excepting sulfur, reduce, then theseelements will not be able to go into solution or to form chemicalcompounds or eutectics with the iron or steel and will remain in theiroriginal oxidic or chemical compound form and will exist in the finishedproduct, after it, has been consolidated and mechanically deformed, asindividual and discrete inclusions which will not adversely affect theproperties of the finished product, except insofar as their bulk asinclusions, if left in in too large amounts, might do so. Furthermore,it has been found that, since these materials ,have not entered intosolution or into combination with the iron, there will be no particulartendency for them to segregate or to form agglomerates within the massof the iron and thus no tendency to cause non-uniformity ordiscontinuity within the finished product.

so In the case of sulfur, which will normally exist during and after thereduction operation as iron sulfide, this constituent having neverbecome molten cannot form the iron-iron sulfide eutectic hereinabovereferred to and cannot be forced to segregate around the grainboundaries and will, therefore, exist as separate inclusions of ironsulfide, 'more or less uniformly dispersed within the matrix of thefinished product. Un-

der these conditions the iron sulfide, instead of 40 causing "hotshortness or brittleness, will impart to the finished product freemachining properties without otherwise seriously impairing its physicalcharacteristics. It has been found in practice that sulfur contents ofslightly over 0.5%

canbe tolerated in a finished steel bar produced in accordancewith thepractice of the present invention without in any way impairing the hotworking characteristics of the material and without noticeably impairingthe physical strength or so ductility of the product.

As an. illustration, sponge iron which, when reduced by the processparticularly described in the' application or James C. Hartley, SerialNo.

338,560, hereinabove identified,- still contained 0.5% of sulfur, wascompacted and sintered after the direct reduction and then hot forged at2200 F. until it was'reduced 90% in area. There was no formation of anyforging cracks or other evidence of "hot shortness as a result of thispro cedure. 1

In thecase ofinclusions of titanium oxide, it has been found in practicethat as much as 1.8% of titanium oxide in iron and steelproductsproduced in accordance with the present invention has no markedlydeleteriouseflect upon the olive Silica up to=2%, as incluicalcharacteristics. sions in iron and steel products made in accordancewith the practice of the. present invention, doesnot' appear to impairmaterially the physi-.

cal characteristics of the product. The toler ance of phosphorus in ironand steel products made in accordance withthe present invention has beenincreased from 0.10%, the maximum, allowable in iron and 'steel productsthat go through a molten stage, to 1.25%.

Not only does the present invention contemplate the manufacture of ironand steel products in which some or all of the elements hereinabovereferred to are found in the ores from which the iron is reduced and areretained as inclusions in the finished products, but, when ores of veryhigh purity are to be utilized in the production of iron and steelproducts and when material having free machining characteristics is desired as an end product, the invention contemplates the addition to theore prior to reduction, or to the product of the reduction operationimmedietely subsequent to the reduction, definite 3. A free machiningiron or steel product having, as an inclusion within the matrices ofgrains thereof and in non-eutectic relation to the iron, iron sulfide.

4. An iron or steel product which, both in its unfinished and in itsfinished condition, is substantially tree from the iron-iron sulfideeutectic but containing, as an inclusion, iron sulfide.

5.An iron or steel product which, both in its unfinished and in itsfinished condition, contains substantial quantities of iron sulfide inthe form of a, uniformly dispersed includon not segregated at the grainboundaries.

amounts of iron sulfide or other sulfur compound specification andclaims, applies to that type er reduction operation in which the metaloxide and the reducing agent are brought directly into reactive relationto each other at a reactive temperature that serves merely to bringabout the reduction of the oxide to the metallic state, without theincidental reactions which take place in. the blast furnace wheremelting of both the metal oxide and the most or the census constituentsis an incident of the smelting of the ore.

What is claimed as new is:

1. Au iron or steel product which, both in its unfinished and in itsfinished condition, has, as an inclusion within the matrices of grainsthereof and in noneutectic relation to the iron, 9. compound, other thanmanganese sulfide, of an element of a group consisting of sulfur,phosphorus, titanium, silicon.

. 2. An iron or steel product which, both in its unfinished and in itsfinished condition, has, as an inclusion within the matrices of greinsthereof and in noneutectic relation to the iron, e compound of anelement of a. group consisting of sul fur, phosphorus, titanium,silicon, eeid compound being of the type which would impair the physicalcharacteristics of the product is produced by a process involvingmelting of the iron.

6. An iron or steel product which, both in its unfinished and in itsfinished condition, is substantiaily free from titanium in solution inthe iron, but containing, as an inclusion, titanium i oxide.

7. An iron or steel product which, both in its unfinished and in itsfinished condition, has phosphorus as a constituent but not in solidsolution therewith.

8. An iron or steel product which, both in its unfinished and in itsfinished condition, has phosphorus as e constituent but free from FesP.

9. An iron or steel product which, both in its unfinished and in itsfinished condition, has phosphorus as a constituent but free from theiron-iron phosphide eutectic.

10. The process or producing 'an iron or steelproduct having, as aninclusion Within the metrices of grains thereof and in non-eutecticrelation to the iron, a compound of an element of a group consisting ofsulfur, phosphorus, titanium, silicon, which consists in directlyreducing a finely divided iron ore containing a compound of one of theaforementioned elements and com- Ducting the reduced powder anddeforming it into the desired product, all at a temperature below thetemperature oi fusion of the iron or of said compound.

JAMES G. HARTLEY. O'I'IO H. KERRY.

